Ideas
+21
Contests: Which subject can win at <Whatever>!
Having a group of contestants all competing. Same equipment rig for each of them, same techniques... but who can take being tickled for the longest? Or balance a ball on their sternum for the longest? Winners could get some kind of prize money, which would not affect your character directly -- it's not your money -- but would make them more likely to return. You could also "cheat" to try and make this happen!
Customer support service by UserEcho
This would be a good idea, but it should have a bigger influence on gameplay, or else just be a fun minigame to earn resources/money. Maybe the winning contestant doesn't win money, but instead wins a slot in the laboratory for a period of time? And for the time that they're in there, they give extra resources/boosted amounts of resources for a period of time before they go home. BUT they only produce these extra resources when you're doing what they asked you to. Maybe from some sort of randomizer, subjects ask for "something new" "tease me" "surprise me" etc.
All great ideas. :)